1. Field of the Invention
The present invention relates to a video processing apparatus and a video processing method, and more particularly to a method for detecting a shot scene based on imaging signals of an imaging apparatus and performing signal processing.
2. Description of the Related Art
An imaging apparatus such as an electronic camera is provided with an automatic exposure control unit for automatically setting the exposure to an optimal value. However, at times such as when shooting a night scene, an appropriate photometric value cannot be obtained because of a large difference in luminance between an object and the background, so that an appropriate exposure cannot be set. Shooting a night scene with an inappropriate exposure setting may cause washed-out colors of neon lamps of the object, resulting in an unnatural image. To solve this inconvenience, detecting a histogram of luminance levels to determine a scene as a night scene from the shape of the histogram has been proposed (see Japanese Patent Application No. 03-263870, hereinafter referred to as a document 1).
With reference to FIG. 2, the night scene determination method according to the proposal in the document 1 will be described below. FIG. 2 is a diagram for describing a histogram for a night scene. In the proposed night scene determination method, a scene is determined as a night scene if the histogram has a distribution mainly consisting of extremely high luminance levels and extremely low luminance levels, like a solid-line histogram shown in FIG. 2. For more accurate night scene determination, control is also performed to determine a scene as a night scene only when the gain is very high or when aperture encoder information indicates a position near the maximum aperture. Once the scene is determined as a night scene, the exposure is controlled to lower the aperture. This allows obtaining an optimal shot image without washed-out colors.
However, the above proposed method has the following inconveniences. For example, a histogram in shooting a backlit scene is also likely to have a distribution mainly consisting of extremely high luminance levels and extremely low luminance levels. A histogram for a high-contrast object can also have a similar distribution. In contrast, a histogram distribution for a somewhat too bright or dark night scene may not fall within expected threshold level ranges. In these cases, the accuracy of night scene determination in the proposed night scene determination method based on the histogram shape of luminance levels is reduced. Consequently, a scene other than a night scene may be erroneously determined as a night scene, or an actual night scene may not be able to be detected as a night scene.